Anything over 200lbs is large by most bike designers standards. They design for racers who are usually well under 200lbs. Given that a 30lb bike is a tank by bike standards but still only 12% of the total combined bike and rider weight for my 220lbs. Thats why I chose durability over light weight. I want my commuter to work everyday without me babying it.
I have an old touring bike that is 30lbs including rack and fenders and a "track" bike that is 22lbs. Neither are light but nor are they a tank. Both are durable and reliable.
I think 32spoke deep section rims are the way to go for a heavy commuter. A low spoke count wheel may hold up but I don't trust them for my daily pounding.
CF is stronger than steel at the same weight or lighter at the same weight, guess which designers chose. In addition CF does not take punishment as well. When CF breaks it tends to shatter. Steel will bend or crack in a slower failure mode with more warning.
Maybe I'm overly cautious or I'm alot rougher on equipment than you, but I would go for a good quality steel frame with 32 spoke deep section Al rims over a CF frame and low spoke count wheels for a commuter. Now for a recreational bike I might make a different choice.
Craig